Light fixtures are, of course, used for a variety of purposes. Beyond simply providing light to enable people to see better, fixtures are also sometimes used for architectural and design purposes, for example to highlight features to provide a desired aesthetic appearance.
For example, in some structures it is desirable to create a large visual hot spot or high point of illumination to draw attention to that area. Accent lighting is used for such purposes.
Wall grazing fixtures, by contrast, are used for different architectural and design purposes, with the light from the fixtures intended to light walls, most effectively textured and three-dimensional surfaces. When used indoors, such fixtures make a room feel brighter because the vertical light levels along the wall lead one to believe that the overall light levels have been increased, and also can add a sense of space. When used outdoors, such fixtures light surfaces to highlight features (e.g., accent the texture of a structure's walls) to impact the overall appearance of the structure to persons passing by.
Whatever the purpose of the lighting, effective lighting will preferably have the light reliably and efficiently directed to provide the desired lighting.
For example, effective wall grazing fixtures will distribute light along the height of the wall, with uniformity of illumination desired between the lowest and highest vertical areas of the wall, which uniformity is hard to define and difficult to achieve. Rather than create large high points such as provided by accent lighting, light from wall grazing fixtures may hit the edges of often multiple textures protruding from the wall to highlight the textures and surfaces, with the effect being to draw attention to large surface areas and the contrast created between the dark areas at the low points and the highlighted areas of the protruding shapes. This is true for both indoor and outdoor applications.
The key to accomplishing the end effect is to create a beam of light which is focused within a narrow beam with the light directed mostly parallel with the wall. Having a wide beam also eases the ability to uniformly light the wall with varying fixture spacing.
Prior art fixtures designed for wall grazing applications (including Kim Lighting's the Wall Director and Commander, IO Lighting's Line, Color Kinetics and Neo Ray's Series 76) use either reflectors or refractors to direct the light away from the light source towards a wall.
For example, Kim Lighting uses reflectors to maximize light from a single ended light source which puts out light in 360 degrees, mainly perpendicular to the axis, with either end of the light source along the main axis emitting little or no light. The lamp is positioned with the main distribution directed through an aperture, without reflection, in a manner to light the intended target, with reflectors parallel with the central axis of the lamp to help lighting efficiency. Further, putting the lamp perpendicular to the wall will distribute light in the farthest direction along a wall (direct light being the most efficient).
Reflectors have also been used to reflect light from the lamp opposite the aperture, as well as to reflect the light which is cut off because it would be considered glare or light pollution, particularly with a high intensity light source and short linear arc tube.
Fluorescent fixtures have used a still different method. The source still emits light in a 360 degree distribution perpendicular to the main axis like a high intensity arc source, though the length of the source is much longer which means that the lamp will perform best when mounted parallel to the wall. Like high intensity sources, light needs to be directed through an aperture towards a wall, requiring that light emitting away from the aperture must be reflected back through the aperture, with light which is cut off to prevent glare and light pollution also reflected to improve efficiency. However, with the 360 degree output of fluorescent fixtures, it is difficult to distribute the light efficiently through the aperture. This results in lost light or large areas of high illumination and large areas of poor light, undesirably creating an uneven lighting wherein only half of the wall is only lit well.
In either of the above scenarios, the optical efficiency ranges between 65 and 80 percent, meaning that 20 percent or more of the light generated is lost before leaving the light fixture.
Light emitting diodes (LEDs) have also been used in light fixtures, such as shown in U.S. Pat. Nos. 7,217,009 and 7,281,818, and by IO Lighting and ColorKinetics. An LED typically emits light in a cone shaped beam (often 120 degrees, generally similar to an incandescent reflector lamp). When such beams are projected with the axis parallel with the wall, the cone shape of distribution can be seen (referred to as a scallop), although scallops can be made to disappear as the cones of light overlap each other if multiple LEDs are used in close proximity.
Further, to improve the amount of light directed parallel with the wall (i.e., to reduce the amount of light which is inefficiently lost as a result of travelling away from the wall to be illuminated), a refractive optic has also been used on the output side of such LEDs. This can, for example, tighten the beam distribution (as measured from Nadir) to 10 degrees (versus, e.g., 120 degrees) if desired (while optics may be used to spread or tighten the distribution, if the desired effect is to get more light further down the wall, using an optic to tighten the beam would be the proper choice).
As previously mentioned, when a cone of light is directed parallel to a wall, the cone of light becomes visible as it is reflected off of the target surface. While theoretically putting LEDs close together could help in causing scalloping from the multiple cones to disappear, how close together LEDs can be placed is limited by the size of any refractive optic used to tighten the beam. As a result, when using individual refractive optics for each LED, it is difficult to light a wall without creating some type of scallop.
To overcome the scalloping problem, a secondary optic has been used to create a lateral distribution which reduces scalloping, but such secondary refractive optic increases cost and lessens efficiency. That is, if the refractive optic is linear and continuous along the center line of multiple LED's (and perpendicular to the axis of the LED distribution), there will be better uniformity so that the cones of light will not be noticeable, but the lateral distribution of the LED will still be, for example, 120 degrees. However, while the 120 degree beam may be suitable for distribution, it does not throw as much light down the wall as the aforementioned system with the individual refractive optics.
The present invention is directed toward overcoming one or more of the problems set forth above.